1. Field of the Invention
The present invention relates to a structure configured to mount a chip component on a substrate and to a module component including such a chip component.
2. Description of the Related Art
For example, a UHF RFID tag antenna typically includes an RFID IC and a dipole antenna that is connected to the two external terminals of the RFID IC, as disclosed in Japanese Unexamined Patent Application Publication No. 2011-517840. In a case in which an IC including such two external terminals without polarity is connected, the two external terminals may be provided at positions that are 180-degree rotationally symmetric to the mounting surface of the IC, so that the IC can be mounted in both 180-degree directions and can achieve the same characteristics.
Recent ICs tend to have a substantially square shape in a planar view to achieve a reduction in size, improvement of handling performance, and improvement of reliability. Therefore, the direction of an IC cannot be determined only by the planar shape of the IC and can be determined only after the pattern of the mounting surface of the IC is checked. Alternatively, it is necessary to attach a marking to determine the direction of the IC, on the upper surface of the IC. In addition, in any case, a mounter needs a step of imaging the mounting surface or the upper surface of the IC and rotating a vacuum chuck so as to set the IC in a predetermined direction, which cannot increase mounting speed.
In contrast, Japanese Unexamined Patent Application Publication No. 2007-102558 discloses a structure in which an IC chip that is an electrical two-terminal component can be mounted and operated even when the mounting direction of the IC chip is at any of 0 degrees, 90 degrees, 180 degrees, or 270 degrees.
However, the structure disclosed in Japanese Unexamined Patent Application Publication No. 2007-102558 has the following problems to be solved.
In the structure in which the terminals on a diagonal line in the IC chip are connected to each other while the two of the four terminals on the circuit substrate are used as floating terminals in a potentially floating state, the ESD current flows through a wiring connection section in the IC chip when static electricity is applied to the floating terminals. However, since the wiring in the IC chip has a high wiring resistance in general, a large current such as the ESD current flows through the wiring in the IC chip, which causes a problem of disconnection of wiring due to the generation of heat.
In a case in which a mounted circuit substrate is a flexible substrate made of a material such as polyimide or a liquid crystal polymer, some of the four terminals may not be securely joined mainly due to deflection of the substrate. Therefore, electric connection failure easily occurs.
The periphery of each of the terminals on the circuit substrate is generally covered with resist in order to prevent a short circuit mainly due to a solder bridge. However, in the case in which a mounted circuit substrate is a flexible substrate made of a material such as polyimide or a liquid crystal polymer, the resist may easily be cracked mainly due to deflection of the substrate, a solder bridge may be caused at a cracked portion, which may cause a short circuit between the terminals. In the structure disclosed in Japanese Unexamined Patent Application Publication No. 2007-102558, while there is no effect on the electrical characteristics even when the connection between the terminals in the diagonal direction is short-circuited, characteristics deterioration occurs when the connection between the terminals is short-circuited somewhere in the longitudinal and lateral directions.
The above described problems occur not only in monolithic semiconductor ICs but also in general surface-mount chip components of which the mounting surface includes external terminals.